1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive employing a non-volatile serial semiconductor memory for storing a control program for a microprocessor.
2. Description of the Prior Art
A disk drive typically comprises at least one microprocessor which executes a control program to implement the various operations of the disk drive, such as host interface, disk interface, caching, servo control, etc. The control program is typically stored and executed from an external non-volatile semiconductor memory, such as a parallel flash. Time-critical code segments of the control program (e.g., servo control) are typically loaded from the external semiconductor memory and stored in a static random access memory (SRAM) integrated with the microprocessor. This allows the microprocessor to execute the time-critical code segments from the SRAM to perform the real-time operations for the disk drive while executing the background code segments (e.g., heroic recovery, data lifeguard, etc.) from the much slower external semiconductor memory. However, the cost constraints of the SRAM typically preclude loading all of the time-critical code segments into the SRAM leading to microprocessor wait states to accommodate the slower external semiconductor memory. In addition, the external semiconductor memory increases the cost of the disk drive by requiring a parallel bus for interfacing with the microprocessor as well as numerous other pins (e.g., numerous power and ground pins to help decrease access time).
There is, therefore, a need to reduce the cost and performance degradation associated with storing and executing a control program from an external semiconductor memory in a disk drive.